Insert bit and holder



Sept. 17, 1957 c. E. FITCH INSERT BIT AND HOLDER Filed April 2, 1953 IN V E TOR. gzzfizwj/ aw $166406; Y

INSERT BIT AND HOLDER ClittordEarl. Fitch, Crete, n1. Application April 2, 1953, Serial No. 346,443 l 1 Claim (Cl. 21949 This invention relates. to insert. bits and, holders therefor.

The. principal object of, this. invention is to provide animprowd insert bit for .a holder, and the combination ther on whichv is simple in construction and foolproof ndi'safe in operation, which may be readily received" and firmly secured in the holder regardless of small relative variations in the dimensions of the bit and the holder, which provides a limited floating relation between the bitandholder, and which permits the application of a large hru t @1116 'lilfre insert bit of this invention is used with. a driving holder having a socket of polygonal cross section in. one end thereofia retaining groove in the socket adjacent the outer end; thereof and a resilient spiltringmounted in the retaining groove. The insert bit has a portion of polygonal cross, section adjacent one end which is received in the, socket of the driving holder between the bottom, of the. socket and the resilient split ring for driving engagementtherein. There is a small clearance. between the, portionof the'bi't of polygonal cross. section,and the socket'to provide a limited floating relation between the two. The insert bit also has a cylindrical portion adjacent the other end thereof which is of smaller transverse dimension than that of the portion of polygonal cross section. A working point is provided on the end of the cylindrical portion for driving a screw or a bolt or the like. The insert bit also has a tapered portion between the portion of polygonal cross section and the cylindrical portion which is engaged along its length by the resilient split ring of the holder to releasably secure the portion of polygonal cross section of the bit in the socket of the holder with the end thereof in engagement with the bottom of the socket. This relationship is at all times maintained regardless of small relative variations in the length of the portion of polygonal cross section of the bit and the depth of the socket in the holder.

As a result the bit is readily received and firmly secured in the holder by reason of the resilient split ring engaging the tapered portion of the bit, maximum thrust can be applied by the holder to the bit because the bit engages the bottom of the socket of the holder, close tolerances between the bit and the holder are not required because of the coaction between the resilient split ring and the tapered portion of the bit, a limited free floating action between the bit and the holder is brought about by the small clearance between the bit and the socket of the holder, and the cylindrical portion of the bit presents a smooth surface which is not likely to catch fingers or clothing during use of the bit thereby providing safe operation.

Further objects of this invention reside in the details of construction of the insert bit and holder and in the cooperative relationships between the component parts thereof.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawing in which:

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Figure 1 is an elevational view of a driving holder with an insert bit secured therein.

Figure 2 is an enlarged sectional view through a portion of thedriving holder taken substantially along the line 2-2 of Figure l and showing the insert bit in elevation.

Figure 3 is a vertical sectional view taken substantially along the line 33 of Figure 2.

Figure 4 is a vertical sectional view taken substantially along the line 4--4 of Figure 2.

Figure 5 is a vertical sectional view taken substantially along the line 5-5 of Figure 2.

Referring first to Figures 1 and 2, a driving holder is designated at 10 audit is provided at one end with polygonal, portions 11 and 12 for reception in a suitable tool such as a power tool for rotating the same. It is provided with a groove 13 for securing the driving holder in the power tool; The driving holder 10 is provided at its other end with a head '14 having a socket 15 of polygonal cross section, the bottom of the socket being designated at 116.. The socket 15 is provided with a retaining groove 17 adjacent the outer end thereof and located in the retaining groove 17 is a resilient split ring- 18,. the splitin the ring being designated 19. To facilitate insertion and removal of the resilient splitring 18 in the retaining groove. 17 the head 14 is preferably. provided with a notch20. The diameter of the retaining groove 17 is larger than the normal diameter of'the resilient split ring 18 so thatthe resilient splitiring: 18 may be expanded substantiallyen-tirely intothe; retaining groove I7; Nor mally,;the resilient. split ring '18 extends: into the: socket 15, but isat all times. retained in place: by the retaining groove 1.7;

The insert bit for receptioni-n the driving holder is designated at. 25; It is provided adjacent one end with a portion of polygonal-cross: section: 26 for; reception socket 15 of the driving holder and this portion 26 of polygonal cross section extends between the bottom 16 of the socket and the resilient split ring 18. The shape of the portion of polygonal cross section 26 is preferably the same as the cross sectional shape of the socket 15 so as to establish a driving relation between the driving holder 10 and the insert bit 25. Preferably, there is a small clearance between the portion 26 of polygonal cross section and the socket 15 so as to provide a limited floating relation between the insert bit 25 and the driving holder 10. This clearance is more clearly shown in Figure 5. The end 27 of the bit 25 engages the bottom 16 of the socket 15 when the insert bit is received in the driving holder.

The insert bit 25 adjacent its other end is provided with a cylindrical portion 28 which is of smaller transverse dimension than that of the portion 26 of polygonal cross section. The end of the cylindrical portion 28 is provided with a working point for driving a screw or bolt or the like. For purposes of illustration the working point is shown to comprise a plurality of flutes 29 for driving Phillips screws or the like. A tapered portion 30 having a gradual taper is located between the portion 26 of polygonal cross section and the cylindrical portion 28, the transverse dimension of the tapered portion 30 gradually decreasing along its length from the portion 26 to the portion 28.

When the insert bit 25 is inserted in the driving holder 19, the portion 26 of polygonal cross section isreceived in the socket 15 of the holder and the inner end 27 of the insert bit engages the bottom 16 of the socket. As the portion 26 is being inserted in the socket 15, the resilient split ring 18 is expanded to permit the insertion. When the inner end 27 of the bit engages the bottom 16 of the socket, the resilient split ring 18 contracts about the gradually tapered surface 30 in order firmly to hold the bit in the driving holder. The point along the tapered portion 30 at which the resilient split ring 18 engages the same is determined by the relative dimensions of the length of the portion 26 of polygonal cross section and the depth of the socket 15, the resilient split ring 18 being adapted to firmly engage the tapered portion 30 at substantially any point throughout its length. As a result, the insert bit 25 is firmly secured in the driving holder regardless of small variations in the length of the portion 26 of polygonal cross section of the bit and the depth of the socket in the holder. In this way it is not necessary to keep close tolerances in the manufacture of the insert bits and the driving holders to maintain the inner end 27 of the bit in engagement with the bottom 16 of the socket. This is automatically compensated for by the coaction between the resilient split ring 18 and the tapered portion 30 of the insert bit.

Because the inner end 27 of the insert bit at all times engages the bottom 16 of the socket, maximum thrust can be applied by the holder 10 to the insert bit 25 which, of course, is extremely beneficial in tightening screws, bolts or the like. Because there is a slight clearance between the portion 26 of polygonal cross section and the socket 15, a limited floating relation is maintained between the driving holder 10 and the insert bit 25 which is also very beneficial in tightening screws, bolts or the like. When the insert bit 25 is received in the holder 10, the only exposed portions of the insert bit are the cylindrical portion 28 and the working point 29 so that a substantially smooth surface is presented which is not likely to catch fingers or clothing during use and, accordingly, safe operation is assured.

While for purposes of illustration one form of this invention has been disclosed, other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and, therefore, this invention is to be limited only by the scope of the appended claim.

I claim as my invention:

In combination, a driving holder having in one end thereof a socket which is of polygonal cross section throughout its length, a retaining groove in the socket adjacent the outer end thereof and a resilient split ring mounted in the retaining groove, and an insert bit having a portion of polygonal cross section adjacent one end received in the socket of the driving holder between the bottom of the socket and the resilient split ring for driving engagement therein, there being a small clearance between the polygonal socket of the holder and the polygonal portion of the insert bit to provide a limited floating relation between the holder and the bit, a cylindrical portion adjacent the other end of the bit which is of smaller transverse dimension than that of the portion of polygonal cross section, a working point on the end of the cylindrical portion for driving a screw or bolt or the like, and a tapered portion between the portion of polygonal cross section and the cylindrical portion of the bit which is engaged along its length by the resilient split ring of the holder to releasably floatingly secure the portion of polygonal cross section of the bit in the socket of the holder with the end thereof in engageemnt with the bottom of the socket regardless of small relative variations in the length of the portion of polygonal cross section of the bit and the depth of the socket in the holder.

References Cited in the file of this patent UNITED STATES PATENTS 428,006 La Dow May 13, 1890 1,774,347 Bainton Aug. 26, 1930 2,150,343 Schieber Mar. 14, 1939 2,239,072 Adams Apr. 22, 1941 2,336,095 Heding Dec. 7, 1943 2,427,260 Cowles Sept. 9, 1947 2,508,459 Hotfsommer May 23, 1950 2,522,217 Fischer et a1 Sept. 12, 1950 2,544,219 Cohen Mar. 6, 1951 2,550,635 Brown et a1. Apr. 24, 1951 2,550,775 Clark May 1, 1951 2,596,594 Petre May 13, 1952 

